Three-Dimensional (“3D”) printing is an additive manufacturing process in which successive layers of material are laid down on top of each other to form a solid 3D object. Over time, various types of 3D printing process have been developed, including extrusion-based 3D printing (e.g., fused deposition modeling (FDM)), and processes based on light polymerization, such as stereolithography (SLA) and digital light processing (DLP), among others.
In stereolithography processes, a 3D structure is built up one layer at a time, with each layer being formed by exposing a photo-reactive resin to an ultraviolet (UV) light source that cures the resin. Note that stereolithography may also be referred to as optical fabrication, photo-solidification, and/or solid free-form fabrication and solid imaging.
More specifically, in a typical stereolithography process, a digital 3D model of an object is created by a user via the software interface of a 3D printing application. The 3D printing application then slices the 3D model with a set of horizontal planes. Each slice of the 3D model can then be converted to a two-dimensional mask image, such that the 3D model is represented as a sequence of two-dimensional mask images, which each outline the shape of the corresponding layer from the 3D model. The mask images sequentially projected onto a photo-curable liquid or powders resin surface while light is projected onto the resin to cure it in the shape of the layer. Alternatively, instead of using masks, each slice of the 3D model may be representing by a two-dimensional image in the shape of the slice, so that a projector can project a sequence of such two-dimensional images onto the resin surface to form an object corresponding to the digital 3D model.